The present invention relates to adjustable wrenches. More precisely the present invention relates to a slide switch controlled movable jaw open wrench.
Adjustable jaw wrenches are well known. A movable jaw slides in a guide track, opposed to a fixed jaw, the jaws comprising an engaging end of the wrench. The guide track is cut in a solid formed housing, while the jaw is adjusted by means of a worm gear that is supported within the housing. Typically the worm gear functions as a thumb wheel wherein rotating the worm gear causes the jaw to move toward and away from the fixed jaw. An improvement to these devices has been to link the worm gear to a slide switch so that moving the switch causes the gear to rotate and the jaw to move.
Two methods to link a sliding switch to a worm gear are typical of the prior art. According to one version, a sliding element links to a helical shaft so that moving the sliding element along the shaft causes the shaft to rotate. A front end of the shaft has a bevel gear or equivalent gear which mates to a respective gear affixed to a common shaft of the worm gear. Thus moving the sliding element causes the worm gear to rotate and the movable jaw to adjust. U.S. Pat. Nos. 3,640,159 and 4,046,034 are examples of a helical shaft type slide adjustable wrench.
Another type of slide adjustable wrench uses a belt or chain around pulleys to link a sliding element to the worm gear. U.S. Pat. Nos. 3,368,432 and 3,901,107 provide examples of this method. In ""432 the belt is directly linked to the worm gear shaft. In ""107 the belt turns an intermediate shaft with a beveled gear linking to the worm gear shaft.
A problem in designing a slide adjustable wrench is to provide an adequate amount of jaw travel within a reasonable range of motion of sliding. The sliding should be a comfortable motion for a user""s finger, not much over about 2 inches if the operating hand is not to be repositioned. Some type of reducing drive system (or more accurately an increasing system) is needed to achieve a useful slide motion relative to jaw motion. One option is to use a steep angle for the cut of the worm gear. However if this angle exceeds by much that used in conventional adjustable wrenches, the jaw will not reliably hold a position under force. Rather the jaw will cause the worm gear to rotate in the manner of a helical driven shaft. A typical effective worm gear using a suitable cut angle needs about 5 to 6 turns to give a full jaw travel. A further option is to employ a reduction at the bevel gear where a shaft meets the worm gear shaft. For example in the helical shaft design of ""034 bevel gear 42 on axle 40 can be smaller than bevel gear 56 on helical shaft 50. At increasing reductions however gear 42 will become impractically small or gear 56 very large. A larger gear 56 will require excess enlargement of the surrounding casing. A related issue is the angle of helical groove 52 in drive shaft 50. A steeper, or more perpendicular, angle of the groove will cause the shaft to rotate faster in relation to the sliding motion of button 54. However the practical steepness is limited by friction to about 30xc2x0 off-axis.
A further problem with a helical shaft design is that such a shaft is not easily produced by simple molding or die casting methods. Such a mold would need multiple elements to avoid under cuts. Thus a good helical shaft is not easily made with low cost.
A belt design must also include some reducing method. For example in ""107 the size of pulley 56 must be minimized. However practical belts limit this diameter to not less than about xc2xc inch, below which strength is greatly compromised. Bevel gear 58 must also be larger than gear 28 as for ""034 above. It so happens that neither reference shows such gears. Empirical testing has shown that these respective designs will not provide adequate jaw motion. A further problem with a belt design is difficulty handling the non-rigid belt during assembly. The design of ""107 provides a complex preassembly fixture as a part of the tool to facilitate handling the belt.
Typical of the prior art is a solid forged housing. It is a well known method to guide and support the movable jaw. Such a housing is reasonable for a conventional adjustable wrench where few components are fitted within. However a slide adjustable wrench requires a large cavity to fit the functional components. Such a cavity requires complex forging or slow cutting operations to form. Another method to form a wrench body is disclosed in U.S. Pat. No. 4,802,390. In this reference laminated plier handles include two sheet metal plates surrounding respective plastic spacers. The spacers hold the metal plates in a spaced and parallel relationship, but do not contain or guide functional components. A plastic sleeve surrounds at least one handle to prevent a user pressing sharp metal edges. U.S. Pat. No. 1,061,046 shows an adjustable wrench with a tubular body formed of a thin non-specific material. The jaw slides in a telescoping arrangement in the body. U.S. Pat. No. 2,514,130 shows a locking plier with a body formed of convoluted sheet metal elements.
There is an opportunity to improve upon the prior art designs in both cost and function.
In the present invention an improved all-gear drive system for a slide adjustable wrench is disclosed. A rack and pinion gear set converts linear motion of a slide switch to rotational motion of a gear shaft. A further drive shaft translates the rotational motion to a worm gear shaft. A laminated steel housing contains a molded or cast body which in turn contains the gears and other components. The gears are discrete rigid elements that are easily handled during assembly and readily held in repeatable positions in use. The gears may be produced by low cost molding, powder metal, or die casting methods. A gear rack is slidably fitted in a channel of the body and linked to the slide switch. A pinion rotates about a fixed axis within the housing. and mates to the gear rack. A bevel gear is fixed to the pinion below the pinion with the combined assembly forming a pinion gear shaft. The bevel gear is preferably larger in diameter than the pinion with the resulting gear ratio increasing the rotation speed of further driven gears. A drive shaft includes two bevel gears at each end with one end mated to the bevel gear of the pinion gear shaft. The bevel gear at the other end mates with a final bevel gear on a worm gear shaft. The worm gear adjusts and holds a movable jaw in a conventional way. Although numerous gears are involved in operating the wrench of present invention, there are only four geared parts, all of which are conventionally and easily made and assembled. These parts are: the rack, the pinion shaft, the drive shaft, and the worm gear.
The present design is especially practical when the gears are guided and supported by a molded body that is held between metal plates or within a simple cavity of a forged housing. The body includes recesses, ribs, slots and other features to reliably hold the parts in position. This mechanical function of the body is in addition to a spacer function. The multifunction body eliminates the need for expensive forging or cutting of cavities in a solid metal housing.
According to a preferred embodiment of the invention the slide switch includes a top facing element. Then the switch may be accessed by either hand from most any position. Optionally the switch also includes a portion facing at least one side to ease its use from certain positions. The slide switch may link to the internal elements through a narrow top facing slot in the wrench handle.
The wrench handle optionally includes a rubber edge to cover the metal edges. This edge is overmolded onto the plastic body to form a prefabricated composite of the relatively rigid plastic body and the soft rubber edge. The rubber forms a raised edge forming ribs around the body to provide a recess into which fits the thickness of the metal plates. According to the invention the rubber edge is closely fitted to and covers the metal edges while being secured by the plastic body. Optionally the edge may be of the same material as the body but still be raised to form a recess for the metal plates forming a smooth continues transition between the metal sides and the plastic edge.